Crack formation in epitaxial [110] thin films of YBa₂Cu ₃O_7-δ and PrBa₂Cu₃O _7-x on [110]SrTiO₃ substrates

A characteristic feature of epitaxial [110] thin films of YBa 2Cu3O7-δ and PrBa2Cu 3O7-x on [110]SrTiO3 substrates is that the films have a tendency to crack along the (001) planes. We have studied the crack spacing as a function of deposition temperature and film thickness. The experimental data have been found to be in excellent agreement with a theoretical analysis of the crack spacings in brittle films. The study has allowed us to determine the critical thickness below which no cracks are expected to form as a function of temperature for [110] films of YBa 2Cu3O7-δ, PrBa2Cu 3O7-x, and YBa2Cu3O 7-δ/ PrBa2Cu3O7-x bilayers.